지도제작 대회

제주도 높이 지도

제주도를 따로 떼어내서 제주도 높이(고도) 지도를 제작해보자.

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한국 R 사용자회

1 대한민국 고도

1.1 sf

코드
library(tidyverse)
library(rnaturalearth)
library(elevatr)
library(terra)
library(sf)
library(stars)

korea_map <- ne_countries(type = "countries", country = "south korea", scale = "medium", returnclass = "sf")

korea_map %>% 
  ggplot() +
    geom_sf()

1.2 tidyterra

코드
library(tidyterra)

korea_dem <- get_elev_raster(locations = korea_map, z = 5, clip = "locations") 

names(korea_dem) <- "대한민국"

korea_dem_tbl <- as.data.frame(korea_dem, xy=TRUE) %>% 
  as_tibble() %>% 
  set_names(c("x", "y", "elevation"))

int_elevation <- classInt::classIntervals(
    korea_dem_tbl$elevation,
    n = 5,
    style = "equal"
)$brks %>% as.integer(.)

ggplot() +
  geom_spatraster(data = rast(korea_dem)) +
  facet_wrap(~lyr) +
  theme(
    legend.text.align = 1,
    panel.spacing.x = unit(0, "lines"), axis.title.x = element_blank(),
    axis.text = element_blank(), axis.ticks = element_blank(),
    axis.title.y = element_blank(), plot.title = element_text(
      hjust = 0.5,
      size = 18, face = "bold"
    ), strip.background = element_blank(),
    strip.text = element_text(size = 14, color = "black", face = "bold"),
    legend.text = element_text(size = 10, family="D2 Coding"),
    legend.title = element_text(hjust = 0.1, size = 16, face = "bold"), 
    panel.background = element_blank()
  ) +
  scale_fill_gradient2(
     low = "grey40",
     mid = "white",
     high = "blue",
     midpoint = 448, # 한반도의 평균 고도는 약 448m 정도로 동아시아 전체 평균(910m)에 비하면 현저히 낮다.
     guide = "colourbar",
     na.value = NA, 
     breaks = int_elevation,
     labels = scales::label_number(suffix = " m", big.mark = ",")
  ) +
  scale_y_continuous(labels = scales::comma) +
  labs(fill = "높이") +
  coord_sf(crs = 4326)

2 제주도 추출

코드
city <- "Jeju Korea"
target_border <- osmdata::getbb(city)

get_bbox <- function() {
    bb <- sf::st_sfc(
        sf::st_polygon(
            list(
                cbind(
                    c(
                        target_border[[1]],
                        target_border[[3]] - 0.2,
                        target_border[[3]] - 0.2,
                        target_border[[1]],
                        target_border[[1]]
                    ),
                    c(
                        target_border[[2]],
                        target_border[[2]],
                        target_border[[4]]-0.5,
                        target_border[[4]]-0.5,
                        target_border[[2]]
                    )
                )
            )
        ),
        crs = "+proj=longlat +datum=WGS84 +no_defs"
    )
    return(bb)
}

bb <- get_bbox()

bb %>% 
  ggplot() +
    geom_sf()

jeju_rasters <- map(korea_dem, ~terra::crop(.x, terra::vect(bb)))

jeju_rasters[[1]] %>% 
  ggplot() +
    tidyterra::geom_spatraster(data = jeju_rasters[[1]]) +
    theme_void() +
  theme(
    legend.text.align = 1,
    panel.spacing.x = unit(0, "lines"), axis.title.x = element_blank(),
    axis.text = element_blank(), axis.ticks = element_blank(),
    axis.title.y = element_blank(), plot.title = element_text(
      hjust = 0.5,
      size = 18, face = "bold"
    ), strip.background = element_blank(),
    strip.text = element_text(size = 14, color = "black", face = "bold"),
    legend.text = element_text(size = 10, family="D2 Coding"),
    legend.title = element_text(hjust = 0.1, size = 16, face = "bold"), 
    panel.background = element_blank()
  ) +
  scale_fill_gradient2(
     low = "grey40",
     mid = "white",
     high = "blue",
     midpoint = 448, # 한반도의 평균 고도는 약 448m 정도로 동아시아 전체 평균(910m)에 비하면 현저히 낮다.
     guide = "colourbar",
     na.value = NA, 
     breaks = int_elevation,
     labels = scales::label_number(suffix = " m", big.mark = ",")
  ) +
  scale_y_continuous(labels = scales::comma) +
  labs(fill = "고도") +
  coord_sf(crs = 4326)

3 (고해상도) 제주도

코드
korea_high_dem <- get_elev_raster(locations = korea_map, z = 10, clip = "locations") 
korea_high_dem %>% 
  terra::writeRaster("data/EDM/korea.tif")
코드
korea_high_dem <- terra::rast("data/EDM/korea.tif")

jeju_rasters <- map(korea_high_dem, ~terra::crop(.x, terra::vect(bb)))

jeju_rasters[[1]] %>% 
  ggplot() +
    tidyterra::geom_spatraster(data = jeju_rasters[[1]]) +
    theme_void() +
  theme(
    legend.text.align = 1,
    panel.spacing.x = unit(0, "lines"), axis.title.x = element_blank(),
    axis.text = element_blank(), axis.ticks = element_blank(),
    axis.title.y = element_blank(), plot.title = element_text(
      hjust = 0.5,
      size = 18, face = "bold"
    ), strip.background = element_blank(),
    strip.text = element_text(size = 14, color = "black", face = "bold"),
    legend.text = element_text(size = 10, family="D2 Coding"),
    legend.title = element_text(hjust = 0.1, size = 16, face = "bold"), 
    panel.background = element_blank()
  ) +
  scale_fill_gradient2(
     low = "grey40",
     mid = "white",
     high = "blue",
     midpoint = 448,
     guide = "colourbar",
     na.value = NA, 
     breaks = int_elevation,
     labels = scales::label_number(suffix = " m", big.mark = ",")
  ) +
  scale_y_continuous(labels = scales::comma) +
  labs(fill = "고도") +
  coord_sf(crs = 4326)